100% relative humidity. Assume a pressure of 1.0 atm (a) Find the rate of extrac

Question

100% relative humidity. Assume a pressure of 1.0 atm (a) Find the rate of extraction of condensate m Q. 4-24 kg/min cond (b) Find heat extraction rate from the air 0 2) (10% each) 0.50 kg/s of steam at 200oC and 800 kPa enters an open feedwater heater operating at steady state. A separate stream of liquid water enters at 800 kPa and 30oC. At the exit the mixture is saturated liquid at 800 kPa. a Find the enthalpy of the 30C liquid h kJ/kg (t 0.05 kJ/kg) b) Find the mass flow rate at the exit in kg/s. m exit kg/s C+ 0.01 k 3) (10% each) 0.02 kmols of gaseous H2(g), is air at 25°C in an experimental motor. Assume complete combustion and that the exhaust is at 1.0 bar. Find the following: a) Air fuel ratio on a mass basis AF b) The dew point of the exhaust Tp C 0.5 °C) 4) (10% each) Consider a gaseous mixture that is 70% N2 and 30% Co2 by volume Assuming an iden 1

Explanation / Answer

3)

H2 + 1/2*(O2+3.76*N2) = H2O + 1.88 N2

Moles of H2 = 0.02 kmols

Since the combustion is completed

Moles of O2 = 0.01 kmoles

Moles of Air = 0.0476 kmoles

Mass of air =  0.0476*28.9*1000 = 1375.64

AF Ratio = Mass of air/100 = 13.76

The exhaust Pressure is 1 bar. The exhaust gas is H2O

Dew point temperature is the saturation temperature at the exhaust pressure

Therefore

The saturation temp at P = 1 bar is

Tsat = 99.62 C

Tdp = 99.62 C

4)

P*V = n*RT

P R and T are constant

V = n*K (Where K = R*T/P)

n = mass/Molecular Wt = m/MW

V = (m/MW)*K -----(1)

Let V be the total volume

Volume of N2 = 0.7*V

Volume of CO2 = 0.3*V

From 1

Mass of N2 = 0.7*V*28/K = 19.6*(V/K)

Mass of CO2 = 0.4*V*44/K = 17.6*(V/K)

Mass fraction of N2 = Mass of N2/(Mass of N2 + Mass of CO2) = 19.6/(19.6 + 17.6)

Mass fraction of N2 = 52.69 %

Mass fraction of CO2 = 47.31 %

R of N2 = 8.314/28 = 0.297 kJ/kg-K

R of CO2 =  8.314/44 = 0.189 kJ/kg-K

Rmix = (mN2*RN2 + mCO2*RCO2)/(mN2 + mCO2)

Rmix = (52.69*0.297 + 47.31*0.189)/100

Rmix = 0.246 kJ/kg-K

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